Planographic printing



Jan. 24, 1933. N, DURHAM 1,895,125

PLANOGHAPHIG PRINTING Filed Feb. '2. 1931 a the plate is Patented Jan. 24, 1933 HOBART N. DURHAM, OF JACKSON HEIGHTS, NEW YORK 1' rLAnoenArHIo PRINTING Application filed February 2-, 1931. Serial No. 512,983.

The present invention relates to planographic printing, and more particularly to a novel process of and apparatus for the preparation, moistening, and treatment of the metal plates generally used in planography. i a i Objects and advantages of the invention will beset forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with theinvention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.

The invention consists in the novel parts, construction, arrangements," combinations and improvements herein shown and described.

The accompanying herein and constituting a part hereof, illustrate one embodiment of the invention, and together with the description, serve to explain the principles of the invention.

The single figure of the drawing diagrammatically illustrates the present preferred embodiment of apparatus in accordance with the present invention and is typicalv of the apparatus by which the process of the pres-, ent invention may be carried into effect.

The present invention provides a process and apparatus for the etching of metal plates for use in the planographic printing processes, and the invention has for a further object the ratus for dampening the metal plates during the process of printing, and maintaining them in such a condition that they will'be properly inked and will remain in their original condition throughout long runs.

In accordance with the present invention, which is particularly adapted for use in connection with the planographic printingof metal plates in which the-metal of which formed is different from the metal or alloy of which the, dampening roller is formed, means areprovided for impressing an electric potential on the metal plate and the dampening roller to cause an electric current to be applied to the plate and the roller, for the purpose of neutralizing the electrolytic action induced by the differdrawing, referred to V provision of a process and appa-c ent potentials of theplate and roller when the plate and roller are electrically connected by the etching solution which is supplied to the surface of themetal plate by the damp-, v ening rollers or for the purpose ofpreparing the plate for printing or for increasing the life of the plate. In the preferred embodiment of the invention, the dampening rollers and the metal plate are electrically insulated from each other,-in the sense that" there is no metallic conduction between them through the frame ofthe press.

Other features of the invention will be initially pointed out in connection with thefollowing detailed descriptions of the present preferred embodiment ofthe' invention, and p it will be understood that the foregoing gen eral description and the following detailed description are both exemplary and'explanatory but not restrictive of the invention In accordance with the process of the present invention, and during the'normal operation of theprinting press, an electriccurrent' is impressed on the planographic plate and theidampening rollers, the direction of flow of the current, the amount and voltage of the current being so regulated that the electromotive force induced by the difference in the" metals of which the plate and dampening rollers are made is completely neutralized, or is neutralized to such an extent thatno" appreciable electrolytic action takes place betweenthe metal planographic plateand the rollers of the dampening mechanism, notwithstanding the fact that they are elec- 'trically connected by the electrically-conducting etching solution employed for dampening. 1

Further in accordance withthe process of the present invention, the planographic plates may be. etched, to condition them for inkin g, after beingplaced on the printing press, and for this purpose, the inking rollers of the press, are placed out of contact with the planographic plate, and the plate cylinder of the press is slowly revolved in the press, contacting with the dampening apparatus, and electrically connected with the metal dampening roller by the electrically-conducting etching solution, while acurrent is passed 9 planographic plate or formed of the same metal, as is sometimes the case, the current may be passed from the planographic plate to the dampening roller, to electrodeposit a thin film of relatively porous, avata -receptive, ink-rejecting metal on the non-printing portions of the plate, which are not covered with the resist or hzwenet taken ink during the-rolling up of the plate.

If, during the operation of the press, and after a great many impressions have been taken from the plate, the plate istaking ink in tho se portions which are intended to be ink-rejecting, or if the ii'npressions are too heavy, the current appliedto the plate may be adjusted to such a value that the waterrecep'tive portions of the plate are etched, thus tending to make the impressions'less heavy and to render the non-printing portions of the plate more strongly ink-reject- By using a dampening roller formed of the same metal as the planographic plate being printed, and by adjusting thevoltage and current to such a value that metal is deposit; ed on the waten'receptive areas of the printing plate at an exceedingly slow'r'ate, or by periodically raising the current and voltage to such a'value that metal is removed from the dampening roller and is electro-deposited on the non-printing portions of the plate, the

plates can beprinted indefinitely, as. the met a]. -worn away during the printingprocess will be replaced by the electro-depositi-on process and 'willaccurately conform to the shape of the original design on the phat-e.

'Referring now in detail to the present preferredembodiment of the app'aratus'a'ccording tothe present invention", and by which 'the processes of the present invention may be carried out, there is provided an impres sioncylinder 10, cooperating with a plate cylinder 11, carrying the metalplanographic plate, a-ll'of which maybe of conventional construction. The inking apparatus inking the printing portions, or ink-receptive portions of the metal planographic plate may also be of conventional construction, and,

preferably "comprises a plurality of inking rollers 12 movable toward and from the plate cylinder and normally contacting with the plate and rolling thereover as the plate cylinder rotates, the inking rollersreceiving their ink froman ink fountain 13 by means of afpe riod'icallyoscillating ductor roller 1%.

The dampeningmechanism, according to the present invention preierahly'con'sists of a pair ofcomposition, or fabric-covered rollers 1'5' contacting with the surface of the planogra phi'c plate and "rolling thereover as the plate cylinder rotates, the dampening rollers also, contacting with 'ametal dampening roller 16 which receives the etching solution to be applied to the surface of the rollers 15 and then to the surface of the plate, from a fountain 18 by means of a ductor roll- Means are also'providecl for controlling the current normally flowlng between the dampening roller and the metal planographic plate for preventing electrolytic action be- .tweenthe plate and roller, in case they are made of different materials, or for etching the :metal planographic plate or electrolytic action between the plate and the roller, in case er 19 which periodically oscillates between 70 the fountain rollerQO and the dampening roller 16.

they are made of different materials, or for etching the metal'planographic plate or-electrodepositing metal on the planographic-plate in accordance with the process set forth I above. As embodied, and for the purposeof enabling a neutralizing current to be setup b'etweenthe metal plate and the dampening roller 16, the dampening roller is mounted on an insulated shaftQl, or'isinsulated from the shaft by which it is rotatably mounted.

Means are'also provided for supplying a stantially constant voltage, such as a storage battery 23, capable of delivering current at about four volts. The potentiometer is preferably provided with two variably positionable contacts 24:. and 25 which canbe posi-e tinned alongthe resistance'independently of each other, one of these contacts (25) being electrically connected with the metal planegraphic plate: on the plate cylinder, the other with the metal surface of the dampening roller 16. By this means, the potential ap plied to the dampening roller maybe minute 1y varied from about +4 to 4: volts, thereby permitting the current to be varied to meet any'ofthe press operating needs; Under normal operation of the press, and for neutralizin'g the electrolytic action between tli dampening roller and the metal planographic plate, due to the fact that these elements are metallically connected, and assuming that a brass dampening roller and an aluminium plate is employed, a 'current'of about 1.6 volts will be-needed across the roller and plate, the positive lead from the. potentiometer being connectedwith the roller, in order to elimina-te slow etching action which the roller would otherwise exert on the plate.

For the purpose of enabling the operator to determine the direction of flow and amount of the current flowing from the plate to the roller, or for determining when the current 7 between the plate and roller is exactly neutralized, a polarized alvanometer or ammeter 27 is preferably lncluded in the circuit from the potentiometer tothe plate and roller, and this ammeter maybe of any form which will show the direction of flow of the current.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What I claim is 1. The process of preparing planographic plates which includes increasing the waterreceptive qualities of the non-printing portions of the plate by electrolytic action while the plate is positioned on the press by which it is to be printed.

2. The process of preventing the electrolytic etching of planographic plates while being printed on a press employing a dampening roller of a metal different from that of the plate which includes neutralizing the gal-.

vanic action induced by the dampening liquid between the plate and the dampening roller.

3. The process of treating planographic plates which includes, placing the plate on the plate cylinder of the press on which it is to be printed, preliminarily etching the plate while on the press, thereafter preventing etching of the plate by galvanic action, and thereafter electrolytically treating the nonprinting portions of the plate to maintain them water-receptive.

4. In a planographic press, a plate supported on a plate cylinder, dampening roller for moistening the plate during the printing operation, said plate and dampening means having an electric current flowing between them and means for neutralizing the electrolytic action between the plate and the roller.

5. In a planographic press, a planographic plate, dampening means contacting with the plate for moistening the plate, said plate and dampening means having an electric current flowing between them and means for controlling the fiow of current between the plate and the dampening means.

6. In a planographic press, a planographic plate, dampening means contacting with the ,plate for moistening the plate, said plate and dampening means having an electric current flowing between them and means for'supplying currentto the plate and dampening means to control the electrolytic action between them.

7. In a planographic press, a planographic. plate, dampening means contacting with the plate for moistening the plate, a source of electric current connected with the plate and dampening means and means for varying the of impressions from printing plates 8. In a planographic press, a planographic platedampening, means contacting with the plate for moistening the plate, and a source of electric current of variablevoltage connected with the plate and dampening means.

9. The process of maintainingthe quality of impressions from planographic plates during long runs, which includes electrolytically replacing the metal worn from the plate by the printing operation during the process of printing. V r

10. The process of maintaining the quality of impressions from metal planographic plates during long runs which includes .de-

positing metal of the same kind as that of which the plate is formed on the plate during the printing operation at substantially the same rate it is worn away by the printing operation. r I

11. The process of planographic printing with a press employing metal plates and dampening rollers which includes impressing an electromotive force on the plate and rollers, and regulating the electromotiveforce in accordance with the operating needs of the press. i

12. In a planographic press, a planographic plate, dampening means contacting with the plate for moistening the plate and including a roller formed of the same metal as the plate and means for depositing metal from the roller on the non-printing areas of the plate.

13. In a planographic press, a planographic plate, dampening means contacting with the plate for'moistening the plate and of impressions from printing plates during long runswhich includes electro-deposit-ing metal on the plate surface during the printing operation to replace metal worn therefrom by printing.

16. Ina printing press, the combination of a printing plate, ametal roller adjacent to said plate and electrically connected with'said plate by means of a liquid conductor, and

-means for impressing an electric potential on said plate and-roller to cause electrodeposition of metal on said plate. 7 y

In testimony whereof, I have signed my name to this specification.

- HOBART N. DURHAM.

voltage and direction of fiow of the current. 

